MIT Builds Artifical Muscles Powered by Water Vapor

A new material developed by engineers at MIT has the potential to act as artificial muscles, or to generate electricity to power micro-electronic devices, simply by absorbing and releasing tiny amounts of water vapor.

This new material is a film constructed from a network of two polymers, polypyrrole (a flexible, yet hard material acting as structural support), and polyol-borate (a gel that swells up as it absorbs water), and the interaction between the two when exposed to water vapor allows this film to change shape and repeatedly curl up and down. By exploiting this continuous action, researchers believe the polymer film could either act as artificial muscles, or be used to generate electricity to power small devices.

"The film harvests energy found in the water gradient between dry and water-rich environments. When the 20-micrometer-thick film lies on a surface that contains even a small amount of moisture, the bottom layer absorbs evaporated water, forcing the film to curl away from the surface. Once the bottom of the film is exposed to air, it quickly releases the moisture, somersaults forward, and starts to curl up again. As this cycle is repeated, the continuous motion converts the chemical energy of the water gradient into mechanical energy." - MIT

Possible uses for this new material include being used as actuators in small robotic devices, as it has been shown to be able to lift as much as 10 times its own weight, or to generate electricity (in conjunction with a piezoelectric material). This could enable advances in environmental or physiological sensors, because the devices wouldn't be dependent on batteries to power them, but could use water vapor from the surrounding environment.

Currently, the polymer film system only generates about 5.6 nanowatts, which isn't enough to power most devices, but it could be used to drive these nano- and microelectronic devices through the use of capacitors to store the generated electricity.